小學(xué)英語(yǔ)語(yǔ)法知識(shí)點(diǎn)：比較while, when, as

　　1）as， when 引導(dǎo)短暫性動(dòng)作的動(dòng)詞。

　　Just as / Just when / When I stopped my car， a man came up to me.

　　2）當(dāng)從句的動(dòng)作發(fā)生于主句動(dòng)作之前，只能用when 引導(dǎo)這個(gè)從句，不可用as 或 while。

　　When you have finished your work， you may have a rest.

　　3）從句表示“隨時(shí)間推移”連詞能用as，不用when 或while。

　　As the day went on， the weather got worse.

　　日子一天天過去，天氣越變?cè)綁摹?/p>